Added benchmarks for the two serialization options in hrpc/mutate.go
Added benchmarks for the two serialization options in hrpc/mutate.go

Tests the speed of serializing both nested maps and structs.

Change-Id: Iec41448856313e7e79d151d7f0687b39a29ec1af

dougklein/gohbase,tsuna/gohbase,dougklein/gohbase,tempbottle/gohbase